This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-156009, filed May 26, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a transfer apparatus and method for transferring a target substrate to be processed such as a semiconductor wafer in a semiconductor processing system. The term xe2x80x9csemiconductor processxe2x80x9d used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
In a process of manufacturing a semiconductor device, a transfer unit is used to transfer a target substrate, such as a semiconductor wafer, between different chambers such as a process chamber and a transfer chamber. A typical transfer unit includes a rotatable and expandable transfer arm having a plurality of arm members rotatably connected to each other. The arm members are constituted of a first arm member, a second arm member, and a pick arm member. The first arm member is rotatably connected to a base of the transfer unit. The second arm member is rotatably connected to the distal end of the first arm member. The pick arm member is rotatably connected to the distal end of the second arm member in order to place a substrate thereon.
When the transfer arm transfers a target substrate, the substrate is not necessarily placed correctly in a normal position on the pick arm member of the transfer arm. Conventionally a method of detecting the amount of positional shift of a target substrate using an optical sensor provided in a given position of a transfer chamber has been known. For example, Jpn. Pat. Appln. KOKAI Publication No. 10-223732 (U.S. Pat. No. 5,917,601) discloses a method of detecting the amount of positional shift of a target substrate when a transfer arm stops in a predetermined position. In this method, an edge of a target substrate on the transfer arm is sensed by an optical sensor and the center of the substrate is obtained from the detected edge.
The above-described conventional method is based on the premise that the transfer arm stops in a predetermined position. More specifically, when the transfer arm stops in the predetermined position, the central position of the substrate stationary on the transfer arm is compared with an ideal central position (normal position) thereof fixed relative to a transfer chamber. Unless the transfer arm stops in the predetermined position, the amount of positional shift of the substrate cannot be detected. In other words, the amount of positional shift cannot be detected in an arbitrary position while the transfer arm is transferring the substrate.
An object of the present invention is to provide an apparatus and a method for transferring a target substrate that are capable of detecting the amount of positional shift of the substrate even when a transfer arm does not stop in a given position.
According to a first aspect of the present invention, there is provided a transfer apparatus for transferring a target substrate in a semiconductor processing system, comprising:
a transfer member including a mount portion on which the substrate is placed;
a driving section configured to drive the transfer member in order to transfer the substrate;
first and second reference portions provided adjacent to the mount portion, the first and second reference portions moving integratedly with the mount portion when the transfer member transfers the substrate;
a storage section configured to store first and second reference values representing distances between the substrate located at a normal position on the mount portion and the first and second reference portions;
a detecting section configured to detect first and second distances between the substrate and the first and second reference portions when the transfer member transfers the substrate; and
a calculating section configured to calculate the amount of positional shift of the substrate from the normal position based on the first and second reference values and the first and second distances.
According to a second aspect of the present invention, there is provided a transfer apparatus for transferring a target substrate in a semiconductor processing system including an airtight process chamber for processing the substrate and an airtight transfer chamber connected to the process chamber through a gate, comprising:
a transfer member provided in the transfer chamber in order to transfer the substrate between the transfer chamber and the process chamber, the transfer member including a mount portion on which the substrate is placed;
a driving section configured to drive the transfer member in order to transfer the substrate;
first and second reference portions which are visible optically and provided adjacent to the mount portion, the first and second reference portions moving integratedly with the mount portion when the transfer member transfers the substrate;
a storage section configured to store first and second reference values representing distances between the substrate located at a normal position on the mount portion and the first and second reference portions;
a detecting section for optically detecting first and second distances between the substrate and the first and second reference portions when the transfer member transfers the substrate;
a calculating section configured to calculate the amount of positional shift of the substrate from the normal position based on the first and second reference values and the first and second distances; and
a control section configured to control the driving section in consideration of the amount of positional shift of the substrate calculated by the calculating section when the transfer member transfers the substrate to the process chamber.
According to a third aspect of the present invention, there is provided a method of transferring a target substrate in a semiconductor processing system, comprising the steps of:
preparing a transfer apparatus, wherein the transfer apparatus comprises a transfer member including a mount portion on which the substrate is placed, a driving section configured to drive the transfer member in order to transfer the substrate, and first and second reference portions provided adjacent to the mount portion, the first and second reference portions moving integratedly with the mount portion when the transfer member transfers the substrate;
storing first and second reference values representing distances between the substrate located at a normal position on the mount portion and the first and second reference portions;
detecting first and second distances between the substrate and the first and second reference portions when the transfer member transfers the substrate;
calculating the amount of positional shift of the substrate from the normal position based on the first and second reference values and the first and second distances; and
controlling the driving section such that the transfer member transfers the substrate in consideration of the calculated amount of positional shift of the substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.